linux-kernel - [RFC PATCH -tip 10/16] x86/disasm: Indicate modified instructions

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Date:	Mon, 02 Apr 2012 01:03:59 +0900
From:	Masami Hiramatsu <masami.hiramatsu@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Huang Ying <ying.huang@...el.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [RFC PATCH -tip 10/16] x86/disasm: Indicate modified instructions

Show modified comment instead of disassembled code when
given instruction has been modified by kprobes or kdb.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu@...il.com>
---
 arch/x86/kernel/kdebugfs.c |   23 +++++++++++++++++++++--
 1 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kdebugfs.c b/arch/x86/kernel/kdebugfs.c
index 5da917d..eccd718 100644
--- a/arch/x86/kernel/kdebugfs.c
+++ b/arch/x86/kernel/kdebugfs.c
@@ -296,13 +296,32 @@ static int disasm_seq_show(struct seq_file *m, void *v)
 	u8 kbuf[MAX_INSN_SIZE];
 	struct insn insn;
 	void *p;
+	int i, ret;
 
+	/* recover if the instruction is probed */
 	p = (void *)recover_probed_instruction(kbuf, (unsigned long)v);
 	kernel_insn_init(&insn, p);
 	insn_get_length(&insn);
 	insn.kaddr = v;
-	snprint_assembly(buf, DISASM_BUF_LEN, &insn, DISASM_PR_ALL);
-	seq_printf(m, "%s", buf);
+
+	seq_printf(m, "%p: ", v);
+	for (i = 0; i < MAX_INSN_SIZE / 2 && i < insn.length; i++)
+		seq_printf(m, "%02x ", ((u8 *)v)[i]);
+	if (i != MAX_INSN_SIZE / 2)
+		seq_printf(m, "%*s", 3 * (MAX_INSN_SIZE / 2 - i), " ");
+
+	/* print assembly code */
+	ret = disassemble(buf, DISASM_BUF_LEN, &insn);
+	if (ret < 0)
+		return ret;
+	seq_printf(m, "%s%s\n", (p != v) ? "(probed)" : "", buf);
+
+	if (i < insn.length) {
+		seq_printf(m, "%p: ", v + i);
+		for (; i < insn.length - 1; i++)
+			seq_printf(m, "%02x ", ((u8 *)v)[i]);
+		seq_printf(m, "%02x\n", ((u8 *)v)[i]);
+	}
 
 	return 0;
 }

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